Radio circuits



Patented July 11, 1939 UNITED STATES RADIO omourrs Aristote Mavrogenis, Camden, N. J.,I assignor to Radio Corporation of America, a corporation of Delaware Original application May 17, 1929, Serial No.

Divided and this application May 20,

1937, Serial No. 143,773

2 Claims.

This invention relates to electron discharge devices having a shielding or screening element, as well as to circuit connections therefor and means for energizing one or more of the elements or electrodes of such electron discharge devices from electric power supply means or source. The auxiliary grid or electrode is'mounted between the anode and the control grid. The voltage difference between the cathode and the auxiliary grid may be of any desired value with reference to the voltage difference between the anode and the cathode.

In this arrangement, the shielding element acts to reduce or counter-balance the electrostatic field between the main anode and the control grid, the field being due to the interelectrodal capacity of the electron discharge device. Such a device, therefore, may be used in radio work as an ampliher in which a higher voltage amplification may be secured under some conditions without the presence of oscillation.

An object of the invention is to devise a screen grid vacuum tube circuit so that the potential between the screen grid and cathode fluctuates similarly in phase to the fluctuations of potential between the anode and cathode.

Further objects of the invention will appear as the description proceeds.

The present case is a division of my earlier application Serial No. 363,833, filed May 17, 1929, issued as Patent 2,092,769, Sept. 14, 1937;

Theinvention is shown in the accompanying drawing, in which the single figure is a diagrammatic view of the invention.

Referring to the drawing, it will be seen that an evacuated vessel or envelope l encloses an equipotential or indirectly heated cathode 2, an anode 3, a control grid 4 and a screen grid 5. The screen grid is interposed between the control grid and the anode and may, if desired, have a portion 5' located beyond the anode in order to shield the anode from the control grid 4 as well as from possible external disturbances. The equipotential or indirectly heated cathode is heated in any desired manner as by. means of the filament 6.

A rectifier is provided which is placed inside the evacuated enclosure. The cathode l of the rectifier is heated by the filament 8 and is connected through smoothing means, including a resistance i0 and condensers H and I2, to one end of a resistance l2. The other end of the resistance is connected to the negative side of the condensers H and I2. The positive sides of the condensers are connected to opposite ends of the resistance H1. The smoothing means, consisting of the resistance and condensers, is connected to one end of the output coil or primary IS, the other endof this primary is connected to the cathode 2 of the signal responsive device.

have any desired voltage impressed thereon by connecting it to a selected point of theresistance l2, as shown in the drawing. As shown in the drawing, the filaments 6 and 8 and the entire The screen grid or accelerating grid 5 may device, in fact, may be directly supplied from the 1,

industrial alternating or direct current mains l4. One side of the mains is connected to the anode Q5 of the rectifier, the other side of the, mains may be connected through a rheostat IE to the smoothing mean'sand to one side of the series-5:

connected filaments 6 and 8, the other side of the series-connected filaments being connected to the anode E5 of the rectifierand, consequently,'completing the circuit back to the other main. The

indirectly heated'cathode lfof the rectifier iso 2 connected to one side of the smoothing means and the smoothing means is connected to the anode 3 of the signal responsive device. .The resistance I2 is bridged around the smoothing means and a selected point thereof is connected:

smoothing means and thus the circuit is completed. As shown in the drawing, the screen grid tube and the circuits therefor are well adapted to be energized from a source of either alternating current or direct current such as the city mains M. Also, as shown in the drawing, the filament or cathode heating means 8' of the rectifier and the filament or heater 6 of the screen grid device are arranged in the same circuit with the resistance I6 and supplied in series from the alternating or direct current mains M.

It will be seen that the anode 3, as shown diagrammatically, is enclosed or surrounded by the electrostatic shielding or screening means 5 and 5. In other words, this anode 3 may be located, as shown diagrammatically, between a plurality of screening or shielding portions, members or elements which may be similar or dissimilar in structure, and which are placed opposite to a plurality of surfaces or sides of the anode 3 and spaced therefrom. Therefore these shielding or screening means are adapted to substantially intercept the electrostatic lines of force extending between the inner and outer sides or surfaces of the anode and some one or more of the elements of the device, such as the control electrode or grid whereby the capacity between the anode 3 and the control electrode 4 or the capacitive coupling thereof is materially reduced or practically obviated.

It will be seen that means, given for illustrative purposes, are provided in the system which enable the screen grid of the tube to be supplied at any suitable positive potential varying from that supplied to the anode or to the anode circuit down to the potential of the cathode, as a variable connection has been illustrated. Obviously, different types of screen grid tubes required different voltages for the. screen grid, but this invention provides any desired voltage for the needs of any particular type of tube to thereby secure the maximum efficiency.

It is to be appreciated that the smoothing means may be located outside of the base of the tube, if desired, and may have any form, a number of forms being disclosed in my original application previously referred to herein.

It is to be understood that the equipotential or indirectly heated cathodes are preferably coated or otherwise associated, with a thermionic oxide so that they will emit electrons at a relatively low temperature, although, obviously, the spirit of the invention will not be departed from if plain uncoated equipotential or indirectly heated cathodes are employed.

It is to be noted, also, that the alternating current source is intended primarily to be the industrial alternating current supply mains, whether connected to the tube through a transformer or any other device or whether connected directly to the tube. It will be noted that provision has been made in this invention for a complete and entire elimination of all batteries if so desired and that the entiire device may be energized from alternating current with the assurance that a stable, satisfactory and reliable condition of operation will be maintained at all times.

While the electron discharge device described above is suitable for alternating current operation, nevertheless, it is well understood that the invention is not to be limited to the use of alternating current for wholly or partially energizing this device, but that the invention will operate also with direct or fluctuating current as well as with alternating current.

In my invention the screen grid is so connected to the load circuit that the potential between the screen grid and the cathode fluctuates similarly in phase to the fluctuations of potential between the anode and cathode. That is, the screen grid voltage has an alternating component of similar phase to the alternating component of the anode voltage.

Having described my invention, what I claim 1s:

1. The combination of an electron discharge device comprising a cathode, a control grid, an anode and a second grid for preventing the anode potentials from appreciably afiecting the anode current over a wide range of anode potentials, means for applying a positive voltage to the anode in respect to the cathode, means for applying a lesser positive voltage to the second grid in respect to the cathode, a load circuit connected between the cathode and anode, an input circuit connected between the control grid and the cathode to control the space current flowing between said cathode and anode, one of said grids having connections to the load circuit for impressing between it and the cathode, fluctuations of potential similar in phase to the fluctuations of potential between the anode and cathode produced by fluctuations of the current flowing through said load circuit.

2. The combination of an electron discharge device comprising a cathode, a control grid, an anode and a second grid for preventing the anode potentials from appreciably aifecting the anode current over a wide range of anode potentials, means for applying a positive voltage to the anode in respect to the cathode, means for applying a less positive voltage to the second grid in respect to the cathode, a load circuit connected between the cathode and anode, an input circuit connected between the control grid and. the cathode to control the space current flowing between said cathode and anode, said second grid having connections to the load circuit for impressing fluctuations of potential between it and the cathode which are similar in phase to the fluctuations of potential between the anode and cathode, produced by fluctuations of I the current flowing through said load circuit. ARISTO'IE MAVROGENIS. 

